Causes, lab diagnosis, and clinical significance of iron deficiency anemia

• Fe deficiency is the most frequent nutritional d/o worldwide

• Most of the Fe is absorbed in the duodenum, and Fe balance is largely maintained by regulation of absorptive intake

• Forms of Fe in the body

  • Functional components

    • About 80% is in Hb

    • Mb and Fe-containing enzymes like catalase and cytochromes contain the rest

  • Storage components

    • Ferritin

      • Protein-Fe complex in liver, spleen, marrow, and skeletal muscle

      • In the liver, most of the ferritin is found in the parenchyma and comes from plasma transferrin

      • Elsewhere, ferritin is found in the macrophages and mostly comes from the breakdown of senescent or damaged RBCs

      • Serum [ferritin] is a good reflection of body Fe stores, but it is an acute phase reactant and it can become elevated with acute inflammation, even with Fe dietary deficiency

    • Hemosiderin

      • Located in lysosomes

      • This is what is mostly stained by special Fe stains (e.g., Prussian blue)

• Causes of (-) Fe balance and anemia

  • Inadequate intake, poor absorption (e.g., sprue, gastrectomy), excessive demand (e.g., pregnancy), or chronic blood loss

  • Chronic blood loss is the most frequent cause in the US and this includes excessive menstrual losses and GI tract loss from ulcers and tumors

• Effects of Fe deficiency are sequential

  • Depletion of storage Fe, followed by decreased serum [Fe] and decreased transferrin saturation (it’s normally 33% saturated), which will show up as a high total plasma Fe-binding capacity

  • Marrow sideroblasts disappear, leading to a microcytic, hypochromic anemia

  • Decreased Hb synthesis leads to elevation of free erythrocyte protoporphyrin (may help tell Fe deficiency from other causes of microcytosis, such as thalassemias and anemia of chronic disease

• Depletion of Fe-containing enzymes may lead to koilonychias, alopecia, and atrophy of the tongue and GI tract mucosa, leading to malabsorption

• Plummer-Vinson syndrome: Fe deficiency anemia, atrophic glossitis and esophageal webs

Category: Medical Subject Notes , Pathology Notes